SAP has this as a step in their upgrade guide to NW04s. See below. I do not think the system I been working on has done any changes to standard here. Where can I see this? I have checked tables TAORA og IAORA but do not see any non standard.

Any other ways to find out if custom DDART classes have been set?

In your SAP BW system, you have set up DDART data classes that do not correspond to the naming
conventions that are described in SAP Note 46272. The data classes are assigned to InfoCubes in the
maintenance transaction RSDCUBE.
The data classes that do not comply with the naming conventions are lost during the upgrade. As a
result, the tables that are generated for an InfoCube cannot be activated correctly and in the technical
settings, an error message about unknown data classes is displayed.
To solve this problem, you can use report RSDG_DATCLS_ASSIGN. It assigns InfoCubes to correct
data classes and enables you to convert groups of InfoCubes from an old (invalid) data class to a
new data class.
You must run the report before the upgrade.